Altered cell–cell adhesion in cisplatin-resistant human carcinoma cells: A link between β-catenin/plakoglobin ratio and cisplatin resistance

Wnt/β-catenin pathway as a potential prognostic and predictive marker in patients with advanced ovarian cancer

Background

β-catenin is the key protein in the WNT signalling pathway and it forms adherent junctions together with E-cadherin. In ovarian carcinoma, abnormal expression of β-catenin, E-cadherin and WNT-1 was observed, but their prognostic and predictive role is unclear. The aim of this study was to clarify the prognostic and predictive role of E-cadherin, β-catenin and WNT-1 in advanced epithelial ovarian carcinoma (AEOC).

Methods

The expression of E-cadherin, β-catenin and WNT-1 was determined by immunohistochemistry in AEOC. The correlation between expression of these proteins and progression-free survival (PFS) and overall survival (OS) was evaluated. Statistical analyses included Kaplan-Meier estimation, log-rank test, Spearman correlation and Cox proportional-hazards model.

Results

In ovarian cancer, intense expression of E-cadherin, β-catenin and WNT-1 was found. In multivariate analysis, strong membrane β-catenin expression was an independent unfavourable predictor for PFS (HR 2.19, 95% CI 1.09-4.39; p = 0.028), while in univariate analysis, strong membrane β-catenin expression was a prognostic factor for OS in patients with AOC (p = 0.039). In multivariate analysis, only resistance to first-line chemotherapy was an adverse independent prognostic factor for OS (HR 16.84; 95% CI 5.07-55.98; p < 0.0001). Additionally, strong membranous β-catenin expression was associated with resistance to platinum-based chemotherapy (p = 0.027).

Conclusions

These findings support that WNT/β-catenin pathway and E-cadherin are important factors in advanced epithelial ovarian cancer.

Increased adenovirus Type 5 mediated transgene expression due to RhoB down-regulation

Adenovirus type 5 (Ad5) is a non-enveloped DNA virus frequently used as a gene transfer vector. Efficient Ad5 cell entry depends on the availability of its primary receptor, coxsackie and adenovirus receptor, which is responsible for attachment, and integrins, secondary receptors responsible for adenovirus internalization via clathrin-mediated endocytosis. However, efficacious adenovirus-mediated transgene expression also depends on successful trafficking of Ad5 particles to the nucleus of the target cell. It has been shown that changes occurring in tumor cells during development of resistance to anticancer drugs can be beneficial for adenovirus mediated transgene expression. In this study, using an in vitro model consisting of a parental cell line, human laryngeal carcinoma HEp2 cells, and a cisplatin-resistant clone CK2, we investigated the cause of increased Ad5-mediated transgene expression in CK2 as compared to HEp2 cells. We show that the primary cause of increased Ad5-mediated transgene expression in CK2 cells is not modulation of receptors on the cell surface or change in Ad5wt attachment and/or internalization, but is rather the consequence of decreased RhoB expression. We propose that RhoB plays an important role in Ad5 post-internalization events and more particularly in Ad5 intracellular trafficking. To the best of our knowledge, this is the first study showing changed Ad5 trafficking pattern between cells expressing different amount of RhoB, indicating the role of RhoB in Ad5 intracellular trafficking.

Evidence of a role for activation of Wnt/beta-catenin signaling in the resistance of plasma cells to lenalidomide

Lenalidomide plays an important role in our chemotherapeutic armamentarium against multiple myeloma, in part by exerting direct anti-proliferative and pro-apoptotic effects. Unfortunately, long-term exposure leads to the development of drug resistance through unknown mechanisms, and we therefore sought to identify pathways that could be responsible for this phenotype. Chronic drug exposure produced myeloma cell lines that were tolerant of the direct effects of lenalidomide, with a degree of resistance of up to 2,500-fold. Gene expression profiling and pathway analysis identified dysregulation of the Wnt/β-catenin pathway as a consistent change across four independent cell isolates, and a pair of primary plasma cell samples. Acute drug treatment also increased β-catenin transcription by 3-fold or more, and both acute and chronic exposure resulted in enhanced accumulation of β-catenin protein by up to 20-fold or more. This produced Wnt/β-catenin pathway activation, as judged by increased activity of a lymphoid enhancer factor/T-cell factor promoter reporter, and enhanced accumulation of the downstream targets cyclin D1 and c-Myc. Components of the β-catenin destruction complex were also impacted by lenalidomide, which suppressed casein kinase 1α expression while augmenting glycogen synthase kinase 3α/β phosphorylation. Stimulation of Wnt/β-catenin signaling with recombinant Wnt-3a, or by overexpression of β-catenin, reduced the anti-proliferative activity of lenalidomide. Conversely, suppression of β-catenin with small hairpin RNAs restored plasma cell sensitivity to lenalidomide. Together, these findings support the hypothesis that lenalidomide mediates activation of Wnt/β-catenin signaling in plasma cells as a mechanism of inducible chemoresistance through effects at the transcriptional and post-translational levels.

Overexpression of cell surface cytokeratin 8 in multidrug-resistant MCF-7/MX cells enhances cell adhesion to the extracellular matrix

Accumulating evidence suggests that multiple complex mechanisms may be involved, simultaneously or complementarily, in the emergence and development of multidrug resistance (MDR) in various cancers. Cell adhesion-mediated MDR is one such mechanism. In the present study, we initially observed increased cell adhesion to extracellular matrix proteins by the MDR human breast tumor cell line MCF-7/MX compared to its parental cells. We then used a strategy that combined antibody-based screening technique and mass spectrometry-based proteomics to identify membrane proteins that contribute to the enhanced adhesion of MCF-7/MX cells. Using MCF-7/MX cells as immunogen, we isolated a mouse monoclonal antibody, 9C6, that preferentially reacts with MCF-7/MX cells over the parental MCF-7 cells. The molecular target of 9C6 was identified as cytokeratin 8 (CK8), which was found to be overexpressed on the cell surface of MCF-7/MX cells. We further observed that down-regulation of cell surface levels of CK8 through siRNA transfection significantly inhibited MCF-7/MX cell adhesion to fibronectin and vitronectin. In addition, anti-CK8 siRNA partially reversed the MDR phenotype of MCF-7/MX cells. Taken together, our results suggest that alterations in the expression level and cellular localization of CK8 may play a significant role in enhancing the cellular adhesion of MDR MCF-7/MX cells.